Israeli troops boarded a Gaza-bound ship attempting to break through Israel’s blockade of the Hamas-ruled seaside strip.

Six Israeli naval vessels stopped the ship, Estelle, Saturday when it was about 30 nautical miles from Gaza.

Masked soldiers boarded the ship and ordered it to sail to Israel's Ashdod port, said a spokesperson for the pro-Palestinian activists on board, one of whom is a former Canadian MP.

Jim Manly, a 79-year-old former NDP MP, was one of about 30 people on board the Swedish-owned ship. Estelle left Naples, Italy on Oct. 7 with individuals from 30 countries, including Israeli activists along with lawmakers from Norway, Sweden, Greece and Spain.

Manly's son issued a statement Saturday afternoon saying his father, a retired United Church minister, was in Israeli custody.

"While he is in good health for his age, he is not as resilient as he was in his youth and has medication he needs to take daily. I hope that the Israeli Defence Forces respect his human rights and legal rights and treat him with the respect and dignity he deserves," said Paul Manly in a statement.

Jim Manly's wife Eva has said her husband was on the Gaza-bound vessel to bring attention to "the suffering of the Palestinians of Gaza."

“He is there out of a commitment to human rights and social justice,” she wrote in a statement. “He hopes to bring awareness to Canadians about what is being done to the Palestinians in the name of Israeli security.”

Eva Manly said she lost contact with her husband early Saturday morning.

"It's hard to imagine what threat one sailboat, loaded with humanitarian supplies and a small number of people, could do to Israel's mighty military,” she said.

A spokesperson for the activists said the ship was carrying cement, basketballs and musical instruments. It was emblazoned with "Ship to Gaza" on one side, and also flew the red, green, black and white Palestinian flag.

Israeli officials maintain that they need to enforce the blockade to prevent weapons smuggling.

Israeli Prime Minister Benjamin Netanyahu issued a statement praising the military for enforcing the blockade. He said there "is no humanitarian crisis in Gaza" and accused the activists of trying to "to provoke and slander Israel's name."

An Israeli military spokesperson said the blockade is in place to prevent weapons from reaching “terror organizations inside Gaza.”

Israel closed Gaza's borders more than five years ago after Hamas seized control of the region and drove out forces loyal to Palestinian President Mahmoud Abbas.

Israel eased its restrictions after its raid of a Turkish-led flotilla en route to Gaza in 2010 left nine activists dead and sparked international condemnation.

The country’s Defence Ministry spokesman Joshua Hantman said the goods on board Estelle would be checked before entering Gaza through the Israeli-controlled land crossing, Kerem Shalom.

He added that Israel allows approximately 50,000 tons of goods into Gaza every week. Gaza residents also use dozens of smuggling tunnels linked to neighbouring Egypt to bring in contraband goods, particularly construction materials.

A spokesman for the group Gaza’s Ark, an initiative that challenges the blockade, said the 1.6 million residents in Gaza are being denied their right to freedom of movement.

David Heap, a Canadian who was aboard a flotilla heading to Gaza last year, said being confronted by the Israeli army was frightening.

“It’s always dangerous when you’re facing one of the largest militaries in the world who are not accountable to anybody,” Heap told CTV News Channel on Saturday.

Heap said he last spoke to Manly Saturday morning. Manly said the team on the ship was prepared for the Israeli troops.

“They were doing non-violence training for many days and (Manly) said there was less fear on board the Estelle than there was among party caucuses in Ottawa.”

Heap said Gaza’s Ark will continue its journey to the region every year until Israel ends the blockade.

“The blockade is wrong in international law,” he said. “They’re required under the Geneva Convention to allow normal civilian commerce. It’s one of the many obligations which they don’t respect.”